No problem, let's work through this together. We're starting with 543644 and are subtracting 80621 from it.

Step 1: We'll start by subtracting the digit 1 and the borrow 0 from 4 in column 1 and get 3.
3 is the first digit of our result.

Step 2: We'll start by subtracting the digit 2 and the borrow 0 from 4 in column 2 and get 2.
2 is the next digit of our result.

Step 3: We'll start by subtracting the digit 6 and the borrow 0 from 6 in column 3 and get 0.
0 is the next digit of our result.

Step 4: We'll start by subtracting the digit 0 and the borrow 0 from 3 in column 4 and get 3.
3 is the next digit of our result.

Step 5: We'll start by subtracting the digit 8 and the borrow 0 from 4 in column 5 and get -4.
We add -4 to 10 and get 6 as the next digit of the result.

Step 6: We'll start by subtracting the digit 0 and the borrow 1 from 5 in column 6 and get 4.
4 is the next digit of our result.

So, 543644 - 80621 = 463023.